Last year around £400 million (€450 million) was spent on MEP’s salaries, travel and office costs.

Now a lawyer for the bloc has warned releasing details of how the public money used by eurocrats would put “big pressure” on them.

The lawyer said: “If everything was visible it would impose a big pressure on MEPs” and they wouldn’t be able to do their job properly.

“If everything was under discussion by journalists in a time where everything is discussed on Twitter,” MEPs would be unable to exercise their “free mandate,” the lawyer later suggested.

She added: “MEPs need to be given a space to think.”

Speaking at the European Court of Justice the lawyer said it was “completely untrue” MEPs’ activities were not already visible enough for the public to hold them accountable.

She said the Parliament’s website allowed the public to see what the EU lawmakers are doing in committees, adding the institution was “extremely transparent.”

Her comments come as part of a furious battle between EU officials and journalists after the bloc refused to publish details of their expenses in 2015.

At the time the parliament dismissed the request as it would be “an excessive burden” to provide them with the documents.

They claimed MEP’s expenses numbered in the millions and were kept in paper format in 48 cabinets which were filled “from ceiling to floor.”.

The lawyer said “The filing system is what it is” adding that there were an estimated 900,000 individual pieces of paper for MEPs’ travel expenses between 2011 and 2015.

The EU Parliament proclaimed it had internal controls in place to recover funds that were incorrectly spent.

Speaking to POLITICO, Anuška Delić, a journalist who brought the case, said: “I can’t get over the shock of hearing this.

“We are not demanding data that covers the private lives of MEPs but strictly their professional duties.”

The Parliament also implied that in some cases they didn’t have the documents in question, including the £3,800 (€4,300) a month General Expenditure Allowance which is paid directly into the MEPs’ bank accounts.

The Court did not give a date for when it will rule in the case.

This comes after a British MEP suggested Tony Blair could be behind a “Remain coup” which is trying to disrupt the will of the British people.

The Brexiteer suggested the technique used by Remainers is similar to the way the Labour Party used to work under Blair.

MEP Steven Woolfe, formerly of Ukip, said he did “not want to point the finger” at the former Prime Minister, but insisted Mr Blair was in the position to try to fight against Brexit.

He said: “I have had a feeling for some time there is an attempt at a Remain coup of the Brexit referendum and that it is being orchestrated.

“At the very least, there’s a mad group-think that’s going around with them.

“But when you’re hearing the same phrases, that’s very reminiscent of the way the old Labour Party used to work under Tony Blair.”